In recent years, ink-jet techniques have made remarkable progress resulting in being designated as having photographic image quality together with printer techniques, ink techniques and exclusive recording medium techniques. In accordance with the improvement of image quality, storage stability of ink-jet images has come to be compared with that of silver salt photography, and pointed out are deterioration such as poor bleeding resistance due to migration of a colorant and deterioration such as poor light-fastness and oxidizing gas resistance due to a chemical reaction characteristic to the colorants.
Many proposals have been made to improve the storage stability of dye ink images. As for an recording medium, as disclosed in Japanese Patent Publication No. 2-31673, achieved is improvement of water-fastness and weather-proofing as well as provision of image glossiness, by after providing a layer comprising thermoplastic organic polymer particles on the outermost surface of a recording medium, the thermoplastic organic polymer particles are fused to be formed into a film, resulting in providing a polymer protective layer.
However, on the other hand, ink absorption rate is significantly decreased compared to a porous recording medium mainly comprised of an inorganic pigment when a layer comprising thermoplastic organic polymer particles on the surface layer is provided. Decreased ink absorption rate causes color bleed or beading resulting in deterioration of image quality. Particularly, in recent years, the deterioration of image quality is a big problem, because speed of printers has become faster to answer the demand of high-speed printing.
Images formed by this method can achieve relatively high glossiness, however, they are still insufficient when compared with those of silver salt photography, in addition, are unfavorable because of unnatural appearance due to such as insufficient uniformity of images, lift of images at the boundary between a high density portion and a white background area. Particularly, this phenomenon is significant when pigment ink is employed or thermal fixing is performed without appropriate intervals after printing for faster image formation. To overcome these drawbacks, increasing thermoplastic organic polymer particles in the surface layer is effective, however, problems cannot be solved because of furthermore decrease of said ink absorption rate.
It is the present state that a recording medium provided with a layer comprising thermoplastic organic polymer particles on the surface layer exhibits effects of improving storage stability of images and providing glossiness by thermal fixing after printing, however there may be caused deterioration of image quality due to decreased ink absorption rate or unnatural impression of images due to image density differences, and urgent improvement is still required.
An objective of the present invention is to provide an image forming method employing ink-jet, which results in improved glossiness of a white background without deterioration of image quality nor ink absorption rate.